1. Field of the Invention
The present invention relates to a scanning-type image displaying apparatus for displaying images on a predetermined surface by scanning the predetermined surface with light beams which are modulated based on image information and are emitted from light source means, using scanning means.
2. Related Background Art
Conventionally, liquid crystal projectors or DLP projectors, in which a two-dimensional spatial modulator such as a liquid crystal element is illuminated with light beams from light source means such as a halogen lamp using an illuminating optical system, and light beams from the two-dimensional spatial modulator are projected onto a screen to be observed using a projection lens, are known as projection-type image displaying apparatuses.
In contrast, scanning-type image displaying apparatuses, in which a screen is scanned with laser light modulated based on image information using scanning means such as a micromechanical mirror and an image is displayed on the screen, are known (U.S. Publication No. 2003/0011751, Japanese Patent Application Laid-Open No. 2004-077549, U.S. Pat. No. 5,694,180).
In such a scanning-type image displaying apparatus, it is easy to downsize the entire apparatus because of the absence of an illuminating optical system. In addition, the apparatus is characterized in that, by scanning with laser light, pixel structures doesn't appear as compared to image displaying apparatuses that use two-dimensional displaying elements such as liquid crystal elements, and that it has a wide color reproduction range, so called color gamut.
Among the three patents U.S. Publication No. 2003/0011751, Japanese Patent Application Laid-Open No. 2004-077549 and U.S. Pat. No. 5,694,180, U.S. Pat. No. 5,694,180 discloses a color image projection apparatus and a conversion optical system used therein in which images are displayed using a polygon mirror and a vibrating mirror as scanning means.
In scanning-type image displaying apparatuses, a desired image is displayed by synchronizing the driving of the scanning means and the modulation of the light beam from the light source means that is optically modulated based on image information. Among such apparatuses, it is necessary in color image displaying apparatuses that display color images to control output (quantity of light emission) from light source means that radiate red, green and blue lights in order to adjust white balance.
In particular, when displaying color images using light source means that radiate red, green and blue lights, output ratio of the three-color lights becomes very important. However, no specific configurations have been disclosed regarding a method for controlling output from each light source means.
For instance, in laser beam printers that display images with laser light, semiconductor lasers are commonly used as their light source means. With laser beam printers, to automatically perform light quantity adjustment of laser light has been referred to as automatic power control (APC). To perform APC, in a CAN package of a semiconductor laser, a photodetector (monitor PD) for monitoring light quantity output is disposed in the vicinity of a laser chip which emits laser light. Thus, laser beam printers are configured so that output upon emission of laser light is fed back from an electric output value of the monitor PD to adjust light quantity.
However, there have been no disclosures regarding a ratio of output from a plurality of light source means when a plurality of light source means are used to display color images.
A scanning-type image displaying apparatus for displaying color images by scanning a scanned surface with red, green and blue laser light modulated based on image information from the plurality of light source means (laser light sources) using optical scanning means capable of performing two-dimensional scanning, and for viewing the color images does not require the use of a two dimensional displaying element such as a liquid crystal element, thereby facilitating the display of high precision color images.
However, when scanning with laser light and displaying a color image on the screen, light source means capable of emitting light quantities of red, blue and green lights at an appropriate ratio will be required. Output from a monitor PD (sensor, photo detector) within a conventional CAN package is not the output intended to actually display images. In contrast, the monitor PD can be disposed in accordance with each of the red, blue and green laser to adjust the output ratio. However, this leads to an increase in the number of parts, which in turn makes the entire apparatus more complicated.
The object of the present invention is to provide an image displaying apparatus capable of appropriately controlling an output ratio of a plurality of light source means that emit light beams (laser lights) with different wavelength ranges (red, green and blue) that are optically modulated by image information without complicating the entire apparatus, and also capable of displaying color images with favorable image quality on a predetermined surface.